9ff is a German car tuning company, based in Dortmund, founded by Jan Fatthauer in 2001, specializing in converting stock Porsches into street legal racing machines, either as fully tuned cars,[1][2][3] or selling individual parts or kits.[4] They are best known for building one of the first cars to exceed 400 km/h (249 mph) - the GT9, which is capable of speeds up to 256 mph (412 km/h).[5] The former company, 9ff Fahrzeugtechnik GmbH, filed for bankruptcy in September 2013.[6][7]The 9ff Engineering GmbH, founded in October 2013, continues proceedings.